The Batam Quarantine Office in Riau Islands Province stopped the import of 25 tons of mackerel from Pakistan worth nearly Rp 1 billion proved to contain formaldehyde, an official with the office said.

Head of the Batam Fish Quarantine Office, Ashari Syarief, said that fish importer PT Bintang Nusantara Mulia imported the fish on Feb. 14, 2012 and scheduled to release them to the local market on Feb. 18. A laboratory test conducted by quarantine officials, however, later found that the fish contained formaldehyde.

“They must be either returned to Pakistan or destroyed. Fish containing formaldehyde is dangerous for the human health,” Ashari told The Jakarta Post on Tuesday.

Studies have shown the ingestion of formaldehyde caused vomiting, abdominal pain, dizziness, and in extreme cases can cause death. According to the prevailing quarantine regulation, the fish had to be either sent back to Pakistan or destroyed by the end of February at the latest.

Ashari also said that the fish actually had been imported according to the prevailing procedures and had also come with a certificate of origin and a certificate of health.

“Yet, as we don’t have any memorandum of understanding (MoU) with Pakistan, all the documents must be rechecked and the result indeed was different,” he said.

He added that since the beginning of December 2011, Batam had opened up fish imports from the region. From January until Feb. 20 alone, according to Ashari, a total of 145 tons of fish has been imported from Taiwan, Japan and Pakistan.

However, he added, it was the first time that imported fish containing formaldehyde was found in Batam, although Pakistan was notorious for using the chemical to preserve fish exports.

Nationally, according to Ashari, there have been four cases of tainted fish being imported from Pakistan, namely in Medan (North Sumatra), Jakarta and Batam.

“The Fishery Directorate General through the Foreign Affairs Ministry is to send a letter of warning to Pakistan regarding the fish containing formaldehyde,” Ashari.